1. Field of the Invention
The present invention relates to an image-forming device such as a laser printer, and a process cartridge detachably mountable in the image-forming device.
2. Description of Related Art
A process cartridge can be detachably mounted in an image-forming device such as a laser printer. The process cartridge is provided with: a photosensitive drum on which electrostatic latent images are formed based on image data; and a developing roller for developing the electrostatic latent images into toner images. When the process cartridge is mounted in this image-forming device, the photosensitive drum and developing roller are arranged in opposition to each other and are driven to rotate in prescribed directions. While the photosensitive drum rotates one revolution, an electrostatic latent image is formed on the surface of the drum. When the latent image comes into contact with the developing roller, toner is supplied from the developing roller onto the surface of the photosensitive drum, developing the latent image into a toner image. The developed toner image is then transferred onto paper as the paper is conveyed between the photosensitive drum and a transfer roller disposed in opposition to the photosensitive drum.
Since this type of process cartridge is not provided with its own driving source, a driving source provided in the main body of the image-forming device has to supply a driving force to the process cartridge for rotating the photosensitive drum and the developing roller. Specifically, when the process cartridge is mounted in the image-forming device, a rotary drive member-provided in the image-forming device is engaged with a rotating member in the process cartridge. The driving force of the driving source provided in the image-forming device is transferred to the rotating member via the rotary drive member.
However, when removing the process cartridge from the image-forming device, it is necessary to disengage the rotating member of the process cartridge from the rotary drive member. Hence, the rotary drive member in conventional image-forming devices has been configured to engage with and disengage from the rotating member of the process cartridge, as described in Japanese unexamined patent application publication No. 2002-149037, for example. In this image-forming device, a cover is provided over an opening in the main casing for mounting and removing the process cartridge, and the engaged state of the rotary drive member is switched in association with the opening and closing of the cover so that the rotary drive member is engaged when the cover is closed and disengaged when the cover is open. In other words, when the process cartridge is mounted in the image-forming device and the cover is closed, the rotary drive member is engaged with the rotating member of the process cartridge. When the cover is open, the rotary drive member is disengaged from the rotating members.